646 PROCEEDINGS OF SECTION H. 
40 feet above the river-bed. In a great flood 23,000 acres 
of about the finest land in New South Wales would be 
submerged, and, according to evidence by settlers, would 
be rendered nearly useless by the silting up and killing of 
the finer grasses. The next objection was the terror 
expressed by the settlers of Singleton and Maitland at 
living below such a quantity of water with the dam only 
between them and drowning. Of course, an engineer need 
not take this into consideration, because he would possess 
the assurance that the dam ought,and must, not give away ; 
but as regards those whom it concerns, they are sure to make 
their fears known.: Then arises the question as to the - 
permanence of the effects to be brought about by the dam. 
The Hunter river in flood brings down silt, and the Goul- 
burn sand; and in great floods incredible quantities of 
drift timber come down both. It does not seem excessive 
to reckon that a smart flood brings down one-sixtieth of » 
its volume of sand and silt; and on such a supposition, 
sixty great floods would fill up the reservoir with sand, 
silt, and drift timber. Although this could not happen 
because of the quantity which would be washed out 
through the sluices, still not only is it impossible to wash 
out anything like all the sediment that would be laid 
down by a great flood over 23,000 acres of the submerged 
land, but every smart fresh brings down sediment, and no 
year occurs in which there are not freshes, although great 
floods may only occur at long intervals. If any one suggests 
how is it that the reservoirs made to supply towns with 
water do not silt up, the answer is that they do so, 
but they are generally cases of large reservoirs filled 
by small streams. We are now, however, considering 
the case of a reservoir Yeceiving a large river, and 
instances are not. wanting of reservoirs filled to the 
top of the dams in a few years. Thus the Torrens River 
was dammed at Adelaide to form a lovely sheet of water 
in front of the City, but it is all silted up now to a foot 
or two deep; and the Kowhai River in New Zealand was 
dammed to raise the water for irrigating the plains, and in 
about 8 years it had filled up with shingle to the top of 
the dam. In both cases the sluices were buried, and would 
not work. Also, in Nature of the 13th June, 1901, one 
reads of a great dam in America which burst, causing great 
damage; but it was noticed that three-fifths of the total 
capacity of the reservoir was filled up with sand and siit 
brought down by the river in four and a half years. It 
may be asked, if a reservoir like this is not permanent. 
